corticobulbar pathways

spinomedullary junction

area where most corticospinal fibers cross to opposite side in pyramidal decussation

11

the crossed corticospinal tract travels through the

lateral column** it innervates neurons that control distal muscles

12

uncrossed corticospinal fibers travel in

ventral column

13

lesions to the corticospinal tract lead to

-sensory as well as motor deficits-inability to RAPIDLY match tactile sensation to motor output

14

Most corticospinal tract fibers influence

Aa and Agamma motor neurons indirectly via interneurons, but some fibers from primary motor cortex end monosynaptically on Aa motor neurons of the hand!!!

15

lesions of the corticospinal tract would lead to loss of

irreversible loss of independent (fractionated) finger movements as well as ability to oppose thumb and fingers*** but they can still move hand as a whole

16

Parallel to the corticospinal tract, the corticoreticular fibers...

-modify reticulospinal projections and provide an alternative route for voluntary motor control

17

red nucleus

-caudal magnocellular division of this structure is the origin of the rubrospinal tract-makes corticorubrospinal tract

18

do rubrospinal fibers cross midline? Travel in pyramids?

-rubrospinal efferents cross the midline-rubrospinal efferents do not travel in the pyramids, they travel in the lateral column in the spinal cord

19

describe the sequence of voluntary movement steps

-a decision must be made that a movement is desired-the starting position of the body and target must be determined from proprioceptive, vestibular, and visual or auditory signals-movement must be planned and organized-motor plan has to be initiated and executed-mid-course corrections must be made

20

Integration of sensory information into a motor plan occurs via

-intracortical and thalamocortical circuitry

21

Intracortical connections: area 4

area 4 is innervated by primary somatosensory cortex according to homotopic organization

Thalamocortical information involves

-feedback from basal ganglia and cerebellum that the cortex uses to assist in planning

24

Initiation and execution of movement is commanded by

-primary motor cortex

25

electrical stimulation of area 6 evokes

-coordinated contractions of muscles at multiple joints

26

area 6 lesions produce

-apraxia: difficulty in executing complex movements

27

where are mirror neurons found?

-premotor areas-they fire either when complex movements are performed or witnessed

28

Name the evidence that execution of movement occurs in the primary motor cortex

-increased blood flows to area 4 only when movement is actually performed-neurons in area 4 begin to fire before contraction of the relevant muscle begins-frequency of neuronal firing codes for the amount of force that is needed in the muscle

29

the net effect of supraspinal pathways on motor neurons is

inhibitory

30

the basal ganglia receives input from the _____ and feeds back through the

-receives input from entire cortical mantle -feeds back through the ventral anterior and ventral lateral thalamic nuclei to the prefrontal/premotor cortices

31

the principle function of the basal ganglia is to

-provide a mechanism for the selection of adaptive motor programs for planning and initiating movement

32

corpus striatum

-caudate+ putamen+pallidum

33

striatum

caudate + putamen

34

palidum

-globus pallidus, GPi and GPe segments

35

substantia niagra

-zona compacta, zona reticulata

36

Globus Pallidus internal (GPi) regulates movement of

-trunk and limbs

37

Substantia Niagra (SNr) regulates movement of

-head and eye movement

38

principle function of the basal ganglia

-provide a mechanism for the selection of adaptive motor programs for planning and initiating movement

39

sensorimotor projections from frontal/parietal cortex to the ____

-project to putamen to operate in fine motor control

40

associative: from prefrontal cortex and other association areas to the ___